What best explains the mechanism of hypercalcemia seen in lymphoma patients?

What best explains the mechanism of hypercalcemia seen in lymphoma patients?

• A. Production of PTHrp by neoplastic lymphocytes.
• B. Direct osteolysis from metastasis.
• C. Increased intestinal absorption due to vitamin D intoxication.
• D. Decreased renal excretion of calcium due to kidney failure.

Answer: (A)

Hypercalcemia in lymphoma is often driven by a humoral factor the tumor produces: PTH-related peptide. Neoplastic lymphocytes can secrete PTHrP, which acts on the same receptors as parathyroid hormone. In bone, PTHrP boosts osteoclast activity and bone resorption, releasing calcium into the blood. In the kidneys, it promotes calcium reabsorption, reducing urinary calcium loss. The result is a rise in serum calcium with suppressed endogenous PTH due to feedback. This mechanism explains why calcium levels rise even without direct bone invasion. While other pathways exist in different cancers or conditions, ectopic PTHrP production by lymphoma cells best accounts for this hypercalcemia pattern.

Hypercalcemia in lymphoma is often driven by a humoral factor the tumor produces: PTH-related peptide. Neoplastic lymphocytes can secrete PTHrP, which acts on the same receptors as parathyroid hormone. In bone, PTHrP boosts osteoclast activity and bone resorption, releasing calcium into the blood. In the kidneys, it promotes calcium reabsorption, reducing urinary calcium loss. The result is a rise in serum calcium with suppressed endogenous PTH due to feedback. This mechanism explains why calcium levels rise even without direct bone invasion. While other pathways exist in different cancers or conditions, ectopic PTHrP production by lymphoma cells best accounts for this hypercalcemia pattern.